A problem with the deployment of stent grafts in the aortic arch is that a satisfactory engagement against the interior of the body vessel wall has to be maintained at the same time as matching the curved shape of the aortic arch. Satisfying both constraints involves a compromise in design and conventional stent grafts do not bend satisfactorily around the aortic arch.
Another design constraint is that the proximal end stent should be at least partly bare, i.e. have no graft material thereon, in order that blood flow may be maintained with side vessels.
US 2005/0049674 A1 discloses a stent graft having a proximal end stent which is substantially bare. The distal end of the proximal stent partially overlaps with the proximal end of the second stent. Viewed from the side, the end of the graft material is a straight line connecting the proximal bends of the second stent.
US 2006/0195172 A1 also discloses a stent graft with a substantially bare end stent which partially overlaps the second stent.
Stent grafts are also disclosed in U.S. Pat. Nos. 5,824,037 and 7,294,147 for example.
US 2006/0195177 discloses a stent graft in which stent graft material between two end rings is shaped with a V-recess to allow access to side vessels of the aortic arch.
A recent proposal for stent grafts for curved vessels is the so-called tri-fold device. This offers some improvement over conventional devices, but in certain cases the two most proximal stents can touch each other during deployment, which may cause the curvature of the stent graft to differ from the curvature of the body vessel;